topic six Flashcards
(281 cards)
1
Q
human digestive system
A
2
Q
amylase
A
digests starch
3
Q
peristalss
A
a wave of contraction and relaxation of the longitudinal and circular muscles of the alimentary canal, by which the contents are forced along the tube.
4
Q
when is the mixture of food mixed with acd in the stomach
A
chyme
5
Q
purpose of the stomach acid
A
kills bacteria and starts the digestion of proteins
6
Q
first part of the small intestine
A
duodenum
7
Q
second part of the small intestine
A
ileum
8
Q
what happens in the small intestine
A
the acid passing from the stomach needs to be neutralised so that enzymes in the small intestine can function properly. These enzymes have an optimum pH of neutral to alkaline, and some of them digest fats and lipids: others further digest carbohydrates; and others further digest proteins. By the time your food reaches the end of the small intestine, digestion has been completed and the digested products have been absorbed from the last section, the ileum. The small intestine is where most of the absorption takes place.
9
Q
what does the pancreas secrete
A
amylase, lipase and proteasae
10
Q
what does the liver secrete
A
bile to emulsify lipids
11
Q
what stores bile
A
gall bladder
12
Q
structure of the small intestine
A
a muscular tube of about 6–7 m in humans that lies between the stomach and the large intestine. It can be divided into three parts, namely the duodenum, jejunum and ileum. The inner surface of the small intestine is covered with specialised structures called villi (singular: villus), which increase its surface area by 30–60 fold: this increase in surface area is essential for absorption, which will be discussed later.
13
Q
If you go from outside of the tube towards the inside, you will come across the following tissue layers:
A
serosa
longitudinal muscles
circular muscles
submucosa
mucosa
14
Q
serosa
A
the outermost layer consisting of connective tissue that is in contact with body cavities.
15
Q
longitudinal and circular muscles
A
responsible for peristalsis
16
Q
submucosa
A
connective tissue that supports the mucosa and that contains large veins and arteries which give rise to the capillary bed of the mucosa.
17
Q
mucosa
A
innermost layer forming the soft lining of the tube comprised of epithelium (which lines the lumen of the digestive track), connective tissue and smooth muscle (villi form part of this layer).
18
Q
endopeptidase
A
breaks down proteins into smaller polypeptides
19
Q
lipases and phospholipases
A
break down lipids and phospholipids respectively, to glycerol and fatty acids. In the case of the phospholipid, phosphate is also produced.
20
Q
nucleases
A
break down dna and rna
21
Q
maltase
A
breaks down maltose into glucose
22
Q
lactase
A
breaks down lactose into galactose and glucose
23
Q
exopeptidases
A
remove a single AA from the end of the small polypeptides
24
Q
dipeptidases
A
break down a dipeptide into two amino acids
25
what are the villi
location of absorptionof all the monomers p-roduced by the digestive processes in the small intestine
26
label a villus
27
abosprtion is
the taking in of dgested food substances as well as minerals and vitamins from the lumen of the small intestine into the blood
28
what produces mucus in the small intestine
goblet cells
29
what carries nutrients and vitamins away from the villus
capilary network and lacteal
30
what is the lamina propria
connective tissue of the villus
31
The following molecules, which are the end products of digestion, are directly absorbed by the villi:
Bases and phosphates from nucleic acids
Fatty acids and glycerol
Amino acids
Monomeric carbohydrates, such as fructose, glucose, galactose and ribose.
32
which organs job is detoxifying contimaniants or poisons
the liver
33
where are fats absorbed
into the lymph which which circulates in the lacteal in the centre of the villus
34
where are food molecules, minerals and vitamins absorbed
into the blood or the lymph. To be absorbed into the blood, the molecules need to pass into the capillaries of the villus.
35
Two-step absorption from the lumen of the small intestine into
capillaries and lacteals of a villus.
1. Substances to be absorbed move from the lumen into the epithelial villi.
2. Amino acids and monosaccharides move from the villi into the capillaries and monoglycerides move into the lacteals.
36
when does simple diffusion occur in food absorption
Occurs when molecules are small and are hydrophobic (so they can pass through the phospholipid bilayers). This occurs mostly with the products of lipid digestion.
37
when does facilitated diffusion happen in food absorption
Fructose, glucose and other hydrophilic monomers are moved by protein channels. Be aware, this still requires a concentration gradient.
38
when does active transport happen in food absorption
s needed when the concentrations are lower in the lumen of the small intestine. Thus, the movement needs to occur against a concentration gradient. Glucose, amino acids and some mineral ions are transported out of the lumen in this way, which requires ATP. The cells of the epithelium have many mitochondria that can synthesise ATP for this process.
39
when does pinocytosis happen in food absorption
Draws in small droplets of liquid surrounded by a small section of the phospholipid membrane, as shown in Figure 2. This is most likely to occur with fat droplets in the lumen of the small intestine.
40
The absorption of fats differs from that of carbohydrates because:
Most absorbed fat first enters the lymphatic system, whereas carbohydrates directly enter the blood.
41
why must glucose be absrobed by facilitated diffusion and active transport
Glucose is a large hydrophilic molecule, therefore it cannot pass through the phospholipid bilayer. The only way it can cross the cell membrane is by passing through a protein as would occur during facilitated diffusion and active transport.
42
describe the absorption of nutrients from the lumen of the small intestine to the capillaries?
Nutrients move from the lumen of the small intestine, across the plasma membrane of the epithelial cell; move across the epithelial cell; then cross the plasma membrane on the other side of the cell. The nutrients then move out of the epithelial cell and into the capillary.
43
two different forms of starch
amylopectin (branched)
amylose (linear)
44
what does amylase break down specifically
the α-1,4 glycosidic bonds that connect the glucose monomers in amylose and amylopectin
45
end products after amylase digests starch
maltose, a dimer of glucose connected by α-1,4 bonds, and maltotriose, which is comprised of three glucose molecules also connected by α-1,4 bonds
46
what other bond does amylopectin contain
α-1,6 glycosidic bonds, however, these cannot be broken down by amylase.
47
what is the branching of amylopectin caused by
α-1,6 glycosidic bonds
48
The molecular structure of amylose.
49
Even after the initial catalytic breakdown by amylase, the di- and tri-saccharides produced from the starch molecules are too large to pass through membranes, so
they need to be broken down into monomers (monosaccharides) before they can be absorbed.
50
what parts of starch enter the small intestine
a mixture of maltose, maltotriose and dextrins
51
what are dextrins
very small polymers still containing the α-1,6 glycosidic bond.
52
which enzymes are immbolised in the epithelial cells of the small intestine
maltase, glucosidase and dextrinase
53
All absorbed monomers from food are transported via
the hepatic portal vein from the small intestine to the liver, from there it enters the general circulation.
54
absorbed food (including glucose formed from the breakdown of starch) is first transported by blood to the WHERE before being distributed to the whole body.
liver
55
what is visking tubing
partially permeable cellulose tubing that contains microscopic pores
It allows water, small molecules and ions to pass through freely, but does not allow the movement of large molecules.
56
what is dialysis
the separation of smaller molecules from larger molecules in solution by selective diffusion through a partially permeable (also known as selectively permeable or semipermeable) membrane.
57
waht does the visking tubing represent
the epithelium fo the small intestine
58
the movement of glucose mimics the
absorption of glucose via the epithelial cells, in this case, represented by the dialysis tubing, into the blood supply.
59
shortcoming of the visking tubing model of digestion
it can only account for absorption by diffusion or osmosis, and cannot be used to model absorption by active transport.
60
When the heart pumps blood into the aorta, the main and biggest artery connecting the heart with the rest of the body, it exerts a systolic pressure of between
120 and 200 mm Hg
61
waht does systolic reger to
the part of the heartbeat when the muscle is contracting
62
what does diastolic refer to
When cardiac muscle is relaxing, that part of the heartbeat is called the diastolic portion
63
is diastolic or systolic pressure lower
diastolic
64
two numbers of blood pressure
systole / diastole
65
artery walls can cope with high pressure because
The walls contain elastic fibres formed from elastin protein, which are stretched at every heartbeat when the pressure is highest. When the walls return to their normal shape, this recoil helps to propel the blood forward. Arteries also have muscular walls to help with the propulsion of the blood. Overall, the muscle and elastic fibres present in the wall of the arteries assist in maintaining blood pressure between pump cycles.
66
the role of the arterial muscle is to keep
arteries narrow enough to maintain the high pressure needed to ensure that the blood has the speed and pressure needed to reach all parts of the body.
67
layers of the artery walls
tunica intima
tunica media
tunica adventitia / externa
68
the part of the tunica intimia facing the lumen is lined with
the endothelium
69
tunica intima
This is the innermost layer and is in direct contact with the blood in the lumen. It includes the endothelium that lines the lumen of all vessels; thus forming a smooth, friction-reducing lining.
70
tunica media
This is also known as the middle coat and is mainly made up of smooth (involuntary) muscle cells and elastic fibres arranged in roughly spiral layers. This layer is usually the thickest of the three layers.
71
tunica adventitia
This is also known as the outermost coat and is a tough layer consisting largely of loosely woven collagen fibres that protect the blood vessel and anchor it to surrounding structures.
72
the highest pressure
is systolic
73
what happens in the circular muscles during systolic blodo pressure
The circular muscles surrounding the arteries resist the outward pressure and constrict. This is called vasoconstriction.
74
what happens in the circular and longitudinal muscles during diastolic blood pressure
When the heart relaxes between beats, the pressure in the arteries is lowest: diastolic blood pressure. The smooth muscles surrounding the arteries can also relax, and this called vasodilation
75
smaller arteries branch off in the bdy to supply blood to organs, limbs called
arterioles
76
aterioles have
a higher density of muscle and are more susceptible to the hormonal and nervous control of vasoconstriction and vasodilation
77
stroke volume
the volume of blood pumped out of the left ventricle of the heart during each contraction (or heartbeat).
78
caridac output
the volume of blood the heart pumps through the circulatory system in a minute.
79
Muscle fibers and elastic fibers are essential to the function of arteries. Which of the following layers contains these fibers?
The tunica adventitia
The endothelium
The tunica intima
The tunica media
tunica media
80
how is blood flow moderated in veins
skeletal muscles: When you move around, especially during vigorous exercise, the muscles squeeze the veins like a pump.
valves to prevent backflow
81
when do valves open and close
82
composition of blood
plasma, rbc, wbc, platelets
83
what does plasma carry
proteins
hormones
co2
glucose
vitamins and minerals
84
waht do rbc contain
hemoglobin
85
what do wbc do
part of theimmune system, defend from disease
86
waht do platelets do
involved in the mechanisms that clot blood when blood vessels break
87
the connection betwen arteries anveins is formed by a
capillary network
88
why is a cap network needed
The nutrients and oxygen in blood need to reach each and every cell of the body. However, the size and wall structure of arteries is too big for that purpose. Arteries cannot fit between individual cells if they are large, and they cannot allow for efficient diffusion if there are many cells through which substances must diffuse. Thus, the arteries divide to form smaller arterioles that in turn divide successively to form very fine blood vessels called capillaries. These vessels then fuse together to form venules, and many venules fuse together to form veins
89
how thick are cap walls
one cell thick with a diamter of around 3-4 µm
90
benefit of cap wall being leaky
allows exchange of materials, oxygen and nutrients with cells in tissues and waste products, such as co2 and urea, back into the capillaries to be transproted by blood. wbc can also exit through gaps between endothelial cells
91
The liquid part of blood that passes through the capillary wall, to bathe tissue cells is known as
tissue fluid or interstitial fluid
92
what composes the tissue fluid or interstitial fluid
water, sugars, salts, fatty acids, amino acids, coenzymes and hormones, as well as waste products from the cells. Since tissue fluid containing dissolved nutrients is in direct contact with tissue cells, exchange of materials between cells and fluid, which occurs by diffusion or active transport, is greatly enhanced. After the exchange has taken place, tissue fluid is mostly reabsorbed into capillaries, which ultimately drains into venules
93
What is present in all arterioles that is not present in all capillaries?
Circular smooth muscle cells
94
What is the function of the gaps between the endothelial cells of capillaries?
Permitting exchange of materials between the blood and the tissue cells
95
diagram of the heart
96
what are The tricuspid valve and the bicuspid valves are sometimes called
the right and left atrioventricular valves.
97
how does blood flow through the body
Right side of the heart
Blood enters the heart through the inferior and superior vena cava, with oxygen-poor blood from the body tissues flowing into the right atrium of the heart.
As the atrium contracts, blood flows from the right atrium into the right ventricle through the open tricuspid valve.
When the ventricle is full, it begins to contract. The increased pressure of blood against the tricuspid valve forces it shut. This prevents blood from flowing backwards into the atrium.
As the ventricle contracts, blood leaves the heart through the pulmonary valve, into the pulmonary artery and flows to the lungs where it is oxygenated.
Left side of the heart
The pulmonary vein carries oxygen-rich blood from the lungs into the left atrium of the heart.
As the atrium contracts, blood flows from the left atrium into the left ventricle, through the open bicuspid (also called mitral) valve.
When the ventricle is full, it begins to contract. The increased pressure of blood against the bicuspid valve causes it to close. This prevents blood from flowing backward into the atrium while the ventricle contracts.
As the ventricle contracts, blood leaves the heart through the aortic valve, into the aorta and to the body.
98
Which of these options correctly describes the location and function of the tricuspid valve?
Ensure the one-way flow of deoxygenated blood from the right atrium to the right ventricle.
99
what does the heart being myogenic mea
the heart muscle can generate its own contractions
100
what initiates the heartbeat
the sinoatrial node
101
regular bpm
60-70
102
points essential in heart contraction
103
The propagation through the heart of the electrical signal initiated in the SA node can be summarised as follows:
The SA node sends out an electrical signal that stimulates contraction as it is propagated through the walls of the atria.
The signal then passes via interatrial septum to reach the atrioventricular (AV) node.
From the AV node, the signal is relayed via the bundle of His located in the interventricular septum to the top of each ventricle (confusingly, the top of the heart, or apex, is the bottom-most part where the two ventricles meet in a shape somewhat like a point).
At the top of the ventricles, the signal spreads from the bundle of His (also called the atrioventricular (AV) bundle), to the ventricles via the Purkinje fibres located in its wall.
104
what is the cardiac cycle
refers to the complete sequence of events in the heart from the start of one beat to the beginning of the following beat.
105
pressure and volume change in the cardiac cycle
106
cardiac cycle
1. Atrial contraction begins ( atrial systole) .
2. Atria eject blood into ventricles ( atrial systole) .
3. Atrial systole ends; AV valves close ('lubb' sound).
4. Isovolumetric contraction of the ventricles occurs ( ventricular systole) .
5. Ventricular ejection occurs.
6. Semilunar valves close ('dupp' sound).
7. Isovolumetric relaxation of the ventricles occurs ( ventricular diastole) .
8. AV valves open; passive ventricular filling occurs.
107
Isovolumetric contraction is a term used to refer to
an event occurring at the beginning of systole, during which the ventricles contract with no corresponding volume change. This can occur because the valves are closed. This type of contraction makes the pressure in the heart chamber rise so that the blood can be forced out of the ventricle into the artery in a one-way direction.
108
provide the correct sequence of events for the propagation of the electrical signals initiated in the SA node to the ventricles?
SA node → AV node → Bundle of His → Purkinje fibres → Walls of the ventricles
109
what can signal the SA node to speed up the heart or slow it down
the cardiac accelerator nerve / vagus nervw
110
what monitors blood pressure, pH and co2
cardiovascular centre
111
aaside from changes in blood pressure, pH and co2 that is detected by the cv centre, what is another factor that influences the SA node
epinephrine/adrenaline
112
Epinephrine increases the heart rate by
stimulating the SA node to emit electrical signals at a faster rate as well as by increasing the conduction speed of impulses generated by both the SA and AV nodes.
113
does co2 lower or raise pH in the blood
lower
114
what are atheromas
fatty deposits caused by high blood concentrations of low density lipoprotein in the arteiral walls next to the endothelial cells
115
what does LDL consist of
cholesterol and fats
116
what is thrombosis
the forming of a clot in the blood vessel that can block the blood vessel entirely
117
how is a myocardial infarction caused
blocked coronary artery
The buildup of plaque takes time and, initially, the restricted flow of blood in such an artery will cause pain due to heart cells being deprived of oxygen and nutrients. Medically, the pain is known as angina.
118
types of plaque formation
High blood concentrations of LDL
Diabetes causing high blood glucose concentrations
Smoking and stress causing high blood pressure
Diets containing high levels of trans fats
Recent research indicates that certain infections with bacteria, such as Chlamydia pneumoniae , can also play a role.
119
Cross section of the human skin.
120
what do mucous membranes do
These membranes produce a sticky mucus that contains glycoproteins and lysozymes, enzymes that attack bacterial cell walls. Both types of molecules have antiseptic properties (properties that discourage or prevent the growth of microorganisms). The mucus itself also forms a barrier, trapping organisms which can be killed by white blood cells that are found in the mucous membranes too.
121
musocus membranes
are made up of a surface layer of epithelial cells over a deeper layer of connective tissue. They produce mucus for protection and lubrication.
122
how is clotting done
a cascade of reactions triggered by damage to a blood vessel.
Platelets release chemicals to start these reactions. The first reaction triggers the second reaction by producing a chemical required for the second reaction. This continues through a series of several reactions including up to 12 factors. People who have the most common form of hemophilia are missing clotting factor VIII. Each reaction takes an inactive protein in the blood called a clotting factor and activates it.
The last step of this cascade of reactions is the conversion of fibrinogen, a soluble and inactive clotting factor in blood, to insoluble fibrin. This reaction is catalysed by an enzyme called thrombin which itself had to be activated by the cascade of reactions. The result is a network of fibers that traps red blood cells and platelets to form a scab
123
Clots can form in the coronary arteries and block the flow of blood. Such a clot is called a
thrombus
124
thrombus def
a blood clot that forms in a vessel and remains in the place where it was formed.
125
how does atherosclerosis cause the formation of clots
narrows the lumen of arteries and slows down blood flow; thus increasing the chance of a clot occluding (blocking) a coronary artery. This will lead to certain parts of the heart not receiving any oxygen and nutrients, causing that part of the heart to die, resulting in a heart attack. When a blood clot reduces the amount of blood reaching the heart muscles rather than stopping it completely, it causes angina or chest pain due to heart muscles not getting enough oxygen-rich blood.
126
how does thrombosis of coronary arteries or formation of a clot within the coronary artery start
when the fatty deposit (plaque) in artery walls rupture the lining of the vessel. The clot that began at the site of the rupture can grow larger with time and completely block the artery.
127
the immune system can be divided into
Non-specific immune system involving phagocytes.
Specific immune system made up of lymphocytes and antibodies.
128
types of leukocytes
macrophages: phagocytosis
lymphocyte: recognises antigens
129
B lymphocyte/cell
Firstly, the B cell divides repeatedly through mitosis to create many copies of the B cell that can recognise the antigen. This process is called clonal selection: 'clonal' comes from the fact that mitosis exactly duplicates, or clones, the B cells, and 'selection' comes from the idea that only one type of B cell, the one matching the antigen, has been 'chosen' to divide. some b cells become memory cells
130
Antibodies produced by plasma cells work in two ways:
They can bind to the antigen, which allows phagocytes to recognise and then destroy the pathogen.
They can bind to proteins in the coat of a virus, which will prevent the virus from entering other (human) cells.
131
what changes in numbers of cells after an infection passes
Once an infection has been overcome, the number of plasma cells which produce these specific antibodies will decrease. However, the memory cells remain in the bloodstream and lymph nodes for a long period of time so that if the same pathogen invades the body again, the response will be much faster. This antibody production in response to an infection is called specific immunity. This is the reason you only get chicken pox once, and the reason that vaccines work.
132
Antibody production by B lymphocytes
133
An antigen associates with which part of an antibody?
Variable regions comprised of heavy chains and light chains combined
134
label an antibody
135
Which sequence of events correctly describes the destruction of pathogens in body tissues by phagocytes?
Chemical recognition, amoeboid motion (extension of pseudopodia), endocytosis, enzymatic digestion
136
what do t lymphocytes help with
help B cells complete their function of making antibodies
137
what does APC stand for
antigen presenting cell, that traps the antigen and presents it to the t helper cell
138
Once the antigen has been recognised by the T helper cell,
the immune system is activated to fight against the antigen. It triggers the production of antibodies and activates macrophages and killer T cells, which will engulf and destroy the antigen.
139
what does HIV do
infects and stops t helper cells from functioning.
Since T helper cells are needed to activate B cells to produce antibodies, infection with HIV causes a loss in the ability to produce antibodies which can lead to the development of AIDS (acquired immune deficiency syndrome).
140
how does HIV work
HIV is a retrovirus that has RNA as its genetic material. Once HIV infects a cell through the proteins on the surface of its envelope, it makes a DNA copy from its RNA, with the help of an enzyme called reverse transcriptase. The cDNA that is produced is inserted into the host cell's genome. These days the infection can be slowed down, or even stopped, with the use of antiviral drugs specifically targeting reverse transcriptase activity.
141
symptoms of HIV
high fever
chills
headaches
shortness of bretah
high heart rae
pain in joints
nausea
blueness
fatigue
142
how can HIV be transmitted
Sexual intercourse
Transfusion of infected blood
Sharing of hypodermic needles by drug users
From mother to child during pregnancy, birth or breastfeeding.
143
Anti-retroviral drugs that combat HIV infection target:
Reverse transcriptase of the virus so that it does not reproduce as quickly in the body
144
what is an antibiotic
any substance produced by a microorganism (usually fungi) that can inhibit the growth of other microorganisms
145
Viruses cannot be treated with antibiotics because:
They do not have a metabolism of their own.
146
how was penicillin tested
Florey and Chain infected eight mice with Streptococcus . This bacterium causes pneumonia in mice. Eight mice were kept under identical conditions, but four of the eight were given an injection of penicillin. The four mice that were not treated with penicillin died within 24 hours, but the treated mice stayed alive.
This experiment does not prove a causal relationship but gives a very strong indication that penicillin may have played a role in the recovery of the mice.
The next step was to test the drug on humans. Florey and Chain proceeded to test penicillin on very sick patients with infections. Most survived, and the commercial production of the drug in the 1940s allowed testing on more and more patients; eventually confirming it as a very effective weapon against infections.
147
ethics behind the testing of penicllin
What Florey and Chain did in the 1930s and 1940s would not be allowed today.
Many nations have their own regulating body, but the standards of the US Food and Drug Administration are considered to be among the most strict. These include pre-clinical studies on individual cells and two mammalian species to investigate toxicity before any human trials begin. Clinical trials on humans should begin with testing on healthy subjects to further investigate any possible problems (such as possible side effects, and how quickly the drug is metabolised and excreted from the body) before sick patients receive the drug.
148
adult breathing rate
12-20 times epr min
149
150
purpose of ventilation
maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries. The longer air remains in the alveoli, the lower the concentration of oxygen in that air, thus decreasing the concentration gradient that drives diffusion of oxygen into the blood.
151
which concentration gradients does gas exchange depen don
one gradient of oxygen and another gradient of carbon dioxide
152
In the alveoli – the tiny air sacs of the lungs where gaseous exchange takes place – the oxygen concentration is HIGHER OR LOWER than the concentration of oxygen in the blood that flows past the alveoli.
higher
153
where is the concentration of carbon dioxide the highest, in the alveoli or in the blood flowing past the alveoli
present in higher concentrations in the blood and lower concentrations in the freshly inhaled air in the alveoli.
154
Gas exchange in an alveolus.
155
type I pneumocytes
extremely thin alveolar cells that are adapted to carry out gas exchange, as shown in Figure 2 . They are very flat and thin, increasing the surface area available for diffusion. This also speeds up diffusion by decreasing the distance between the inside of the alveolus and the capillary.
156
type II pneumocytes
secrete a solution containing surfactant, which is a water-based solution containing phospho-lipoproteins. Surfactants create a moist surface inside the alveoli (shown as a film of moisture in Figure 2 ) to prevent the sides of the alveoli from sticking to each other: they do this by reducing surface tension. The moisture also increases the speed gases dissolve, which helps gas exchange.
157
two steps of ventilation
inspiration (breathing in) and expiration (breathing out). Sometimes these two steps are called inhalation and exhalation, respectively.
158
When breathing in
the thorax (the chest) expands and the pressure inside the lungs is lowered, ensuring that thoracic pressure is lower than atmospheric pressure. This causes air to rush into the lungs.
159
When we breathe out
the thorax gets smaller, the pressure rises and the air is forced out of the lungs
160
inspiration
161
expiration
162
Muscles involved in inspiration and expiration.
163
wchich msucles are used in inspiration
external intercostal muscles
164
which muscles are used in expiration
internal intercostal muscles
165
tidal volume
refers to the amount of air which enters or leaves the lungs in a single breath at rest. The average tidal volume is 500 ml.
166
During which stage of ventilation is the diaphragm contracted?
inspiration
167
causes of lung cancer
Asbestos dust particles lodge in the lungs and cannot be broken down
Smoking (cigarettes, cigars, pipe tobacco)
Passive smoking (breathing in someone else's cigarette smoke); about 3% of all cases
Air pollution: diesel exhaust fumes contain many carcinogens (compounds causing cancer)
Radon gas: in some parts of the world there is a higher concentration of this radioactive gas. It emits alpha particles, which can cause mutations when inhaled.
168
consequences of lung cancer
cough
pain
fatigue
shortness of breath
169
what causes emphysema
long-term exposure to cigarette smoke and other pollutants
170
what does emphysema do to the body
It gives rise to an inflammatory (swelling of tissues) response in the lungs, resulting in a narrowing of the small airways and breakdown of lung tissue. There is also evidence that the alveoli become less elastic, making ventilation more difficult. Furthermore, there is increased protease activity, which breaks down the alveolar wall, creating one larger air space instead of many small ones. This reduces the surface area of the lungs and results in a smaller amount of oxygen reaching the bloodstream. Normally, the proteases are inhibited by alpha-1-antitrypsin, but in emphysema patients, the activity of this enzyme inhibitor is reduced.
171
normally, protesases are inhibited by alpha-1-antitrypsin but in emphysema patients,
the activity of this enzyme inhibitor is reduced
172
how many neurosn does the human body have
80-90 billion
173
what is amyelin sheath
an insulating layer that speeds up the transmission of a nerve impulse. This fatty layer is composed of compacted layers of the Schwann cell membrane, which is mostly lipid, but also contains several proteins. These play important roles in maintaining the structure and compaction of the myelin and adhesion of the sheath to the axon.
174
what is the node of ranvier
the gap between the adjacent shwann cells
175
how does the myslein sehath increase speed of nerve impulses
The myelin sheath forces the nerve signal to jump from one node of Ranvier to the next, which accounts for the faster speed of impulse transmission. This is called saltatory conduction of nerve impulses.
176
The nucleus and most of the organelles in a neuron are located in the:
cell body
177
In which direction are nerve impulses propagated along a neuron?
From cell body to axon terminal
178
When a neuron is not transmitting a signal, it has more Na + ions
on the outside of its membrane than the inside, and has more K + ions on the inside than the outside
179
For every turn of the Na + /K + pump, three Na + ions are transferred to the outside, but only two K + ions are pumped back into the neuron. The combination of all of these factors results in the overall loss of positive ions from the neuron, which in turn contributes to the development of the negative resting membrane potential of
−70 mV
180
Depolarisation is caused by
the opening of Na + (sodium) channels which allows the rapid influx of Na + ions (passive movement of Na + ions into the cell).
181
Since there is a concentration gradient across the neuron membrane (there is a higher concentration of Na + ions outside), the change is rapid. The membrane potential of −70
mV changes quickly to a positive value of around
+30 mV
182
Once an area of the neuron has been fully depolarised, the change in potential causes
voltage-gated K + channels to open. Voltage-gated means that the trigger to open the protein channels is a membrane potential of +30 mV.
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what is hyperpolarisation
in many cases, the membrane potential becomes even more negative than the resting potential for a brief period (approximately 2 ms); The reason for this is that not all K + channels close immediately after the resting potential has been reached.
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what happens right after hyperpolarisation
that part of the neuron enters a refractory period and cannot be depolarised (to generate an action potential) as its Na + channels are inactivated.
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threshold potential
-50mV
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Once a neuron is depolarised to about –50 mV,
the depolarisation will rapidly rise to +30 mV and the action potential will occur (that is, a nerve impulse is sent). The –50 mV level is called the threshold potential
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when is an action potential caused
Any depolarisation over the threshold
This is called the all or nothing principle. If a neuron does not reach a threshold potential of around –50 mV, the neuron will not depolarise enough to send an impulse. If it reaches this threshold, there is a positive feedback effect in the membrane, and nearby Na + channels open to further depolarise the neuron and instigate the action potential.
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The threshold potential is
the minimum level to which a membrane potential must be depolarized to trigger an action potential . The threshold potential varies between –55 mV and –40 mV.
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Depolarisation:
Na + channels open, Na + diffuse to the inside of the neuron.
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Repolarisation:
Na + channels close and K + channels open allowing K + to diffuse out.
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Neurons need a threshold potential (around –50 mV), otherwise
the neuron cannot be depolarised: known as the all or nothing principle.
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Propagation of a nerve signal
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what does a synapse consist of
a presyntaptic neuron, post synaptic neuron with a gap on 20nm between them
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waht does the gap in a synapse prevent
movement of a nerve signal from one to another
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The propagation of a nerve signal at a synapse is made up of the following steps
A neurotransmitter is synthesised and stored in vesicles of the presynaptic neuron.
Action potential reaches the presynaptic terminal.
Depolarisation of the presynaptic terminal causes opening of the voltage-gated calcium (Ca 2 + ) channels.
Influx of Ca 2 + through channels.
Ca 2 + causes vesicles (containing neurotransmitter) to fuse with a presynaptic membrane.
Neurotransmitter is released from presynaptic neuron into the synaptic cleft via exocytosis.
Neurotransmitter binds to receptor molecules on postsynaptic membrane.
Opening or closing of postsynaptic ion channels (for example if Na + channels are opened, Na + ions will enter the postsynaptic neuron and depolarise the neuron, possibly initiating an action potential).
Membrane potential of postsynaptic neuron changes (for example, depolarised if sodium channels are opened), which affects whether the postsynaptic cell may have an action potential.
Retrieval of vesicular membrane from plasma membrane in the presynaptic neuron.
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Depending on which channels open, the neurotransmitter may cause the postsynaptic cell to be
excited (depolarised, and closer to threshold) or inhibited (hyperpolarised, and farther from threshold potential).
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Acetylcholine consists of
a choline and an acetyl group
In the presynaptic cell, these are combined by the enzyme choline acetyl transferase and stored in vesicles.
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what does acetylcholinesterase do
breaks down the neurotransmitter into choline and acetate.
The choline is reabsorbed by the presynaptic cell and used again while the acetate is recycled in the presynaptic knob.
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Neonicotinoids are
derivatives of nicotine used as insecticides
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Once a neonicotinoid enters the nervous system,
it binds irreversibly with the receptors, preventing acetylcholine from binding. Additionally, acetylcholinesterase cannot break down these compounds. The effect is that the synaptic transmission is permanently blocked or, in other words, the nerve signals cannot be propagated to the postsynaptic nerve. When this happens in the brain, the result can be paralysis or even death.
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do neonicotinoids affect humans or insects more
insects much more
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Why are humans less affected than insects by neonicotinoids?
Why are humans less affected than insects by neonicotinoids?
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cholinergic receptors
cholinergic receptors
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How do neonicotinoids block synaptic transmission at cholinergic synapses?
How do neonicotinoids block synaptic transmission at cholinergic synapses?
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blood glucose levels
70-130 milligrams/decilitre
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where are insulin and glucagon produced
islets of langerhans
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insulin is produed and secreted from
produced and secreted by β-cells of Islets of Langerhans in the pancreas.
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glucagon is produced and secreted from
produced and secreted by α-cells of Islets of Langerhans in the pancreas.
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insulin Effect on blood glucose concentration
Levels fall : insulin stimulates glucose uptake into muscles and liver cells, where it is converted into glycogen.
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glucagon Effect on blood glucose concentration
Levels rise : Glucagon stimulates glycogen hydrolysis to glucose in the liver, which in turn releases glucose into the blood.
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what is the difference between an exocrine and endocrine gland
As an exocrine gland (gland associated with a duct), it secretes enzymes that help in digestion; while as an endocrine gland (ductless gland) it secretes hormones that regulate blood sugar levels.
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differnece between glucagon and glycogen
Glucagon is a protein-based hormone released from the pancreas. Glycogen is not a hormone: it is a carbohydrate found in the liver that is the form that glucose takes when stored there.
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in pateints with diabetes,
the blood glucose levels are consistently too high and their urine has elevated glucose levels. Other symptoms include frequent urination, increased thirst and hunger.
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type I diabetes
results from the body's failure to produce insulin. Sometimes this form of diabetes is referred to as insulin-dependent diabetes mellitus (IDDM) or juvenile diabetes
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type II diabetes
results from insulin resistance, a condition in which body cells fail to use insulin properly. This form was previously referred to as non insulin-dependent diabetes mellitus (NIDDM), or adult-onset diabetes because it often begins later in life.
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what does thyroxine do
the main hormone that regulates your metabolism and body temperature. It is produced in the thyroid gland. The general effect of thyroxine is to activate nuclear transcription of large numbers of genes for the synthesis of enzymes, structural proteins, transport proteins and other substances in virtually all cells of the body. Therefore, thyroxine increases the metabolic activities of almost all the tissues of the body.
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effects of thyroxine
Increased rate of utilisation of foods for energy
Increased breathing rate to obtain oxygen and get rid of carbon dioxide
Increased rate of protein synthesis and protein catabolism
Increased number and size of mitochondria in most cells of the body
Increased growth rate of children and adolescents
Growth and development of the brain during fetal life and for the first few years of post-natal life
Enhanced carbohydrate metabolism
Enhanced fat metabolism.
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when body temperature is above normal, the thyroxine level is
decreased to reduce cellular respiration, and thus reduce heat production.
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the production of thyroxin requires
four atoms of iodine and the amino acid tyrosine
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what is goitre caused by
iondine deficinecy
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symptoms of thyroxine deficiency
Fatigue
Depression
Forgetfulness
Feeling cold
Constipation.
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If the body temperature drops below normal, the thyroid gland helps to control the body temperature by producing:
more thyroxine
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what are adipose tissues
fatty tissues mainly composed of fat cells (adipocytes) that are specialised in the synthesis and storage of fat globules.
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Two factors control blood leptin concentration:
Food intake
The amount of adipose tissues in the body.
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Leptin receptors are found in the hypothalamus of the brain. Once leptin binds to these receptors, it causes
appetite inhibition
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what happens to the level of plasma leptin when fat mass decreases
it falls so that appetite is stimulated until the fat mass is recovered
There is also a decrease in body temperature and energy expenditure is suppressed.
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Conditions that affect the level of leptin production and action on the body
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mice with two of the recessive alleles (ob) cannot produce
leptin
In further experiments, the ob/ob mice were given injections of leptin and their body mass reduced by about 30% within a month.
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obese people have very high leptin levels in their blood. This implies that
receptor cells in the hypothalamus may no longer be sensitive and responsive to leptin, thus they do not induce appetite inhibition
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Leptin is a hormone that is released from:
adipose tissue
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what is th epineal gland
a small endocrine gland found near to the centre of the brain between the two hemispheres, it is reddish-grey and shaped like a pine cone about 0.8 cm long.
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Melatonin is synthesised from the amino acid
tryptophan and its production is dictated by light. Exposure to light has a negative effect on the release of melatonin.
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the body follows a 24 hour cycle so
Melatonin secretion is generally low when you are exposed to daylight and high during dark periods.
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what is the bodys reaction to a fall in melatonin
your body core temperature drops and receptors in the kidney cause decreased urine production, all of which increases sleepiness
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The first sign of development of reproductive organs occurs during
the 5th week and sexual distinction of the external genitalia becomes apparent in the 10th to 12th week.
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what triggers the development of testis, and indirectly, the procudtion of testosterone
a protein named TDF (Testis Determining Factor), coded for by the SRY gene on the Y chromosome
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how do some fetuses become male
TDF is a DNA-binding protein that regulates the transcription of a number of genes involved in the differentiation of the gonads into the testis. This happens around week 8 of pregnancy. Once the testis have developed they start to produce testosterone. This triggers the development of the male genitalia.
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female reproduction system
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female repdocution system front
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ovary function
Estrogen, progesterone and ovum (egg) production
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fallopian tubes function
Collects eggs from ovary and carries them to uterus
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uterus function
Place for the gestation of the embryo and fetus
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cervix function
Blocks the entry to the uterus during pregnancy and dilates during birth
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vagina function
Canal connecting cervix and outside of body: forms birth canal and is the receptacle for penis during heterosexual intercourse
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vulva function
External parts for the protection of the internal reproductive system
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Male reproductive system side view
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Male reproductive system front view.
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testis function
Sperm and testosterone production
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epididymis function
Stores sperm until ejaculation
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sperm duct function
Transfers sperm during ejaculation
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seminal vesicles function
Produce an alkaline, sugar-rich fluid (fructose) that provides sperm with a source of energy to help them move
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prostate gland function
Produces an alkaline fluid, rich in proteins which together with seminal vesicles' secretion and sperm makes semen
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urethra function
Transfers semen during ejaculation and is the passage of urine during urination
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penis function
Becomes erect during sexual arousal: penetrates the vagina during heterosexual intercourse to deposit semen close to the cervix
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puberty
the phase of adolescence when the individual reaches sexual maturity and becomes capable of reproducing. It is accompanied by maturation of the genital organs, development of secondary sexual characteristics and, in humans and some primates, by the first occurrence of menstruation in the female.
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menopause
the phase in a woman's life (around the age of 45–50) when her menstruation stops
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follicular phase
refers to the formation of follicles in the ovaries. Each follicle contains one egg during its development until ovulation.
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luteal phase
refers to the transformation of a follicle into a corpus luteum once ovulation has taken place around day 14.
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Follicular phase :
FSH causes several follicles in the ovary to begin to develop. Usually, only one matures. As the follicle develops, it secretes estrogen. The estrogen stimulates the uterine lining (endometrium) to thicken with mucus and a rich supply of blood vessels. These changes last about 10 days and prepare the uterus for a possible pregnancy; the endometrium is where a fertilised ovum will implant in order to further develop during pregnancy.
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ovulation phase
A high level of estrogen in the blood (produced by the follicle) causes the pituitary gland to reduce the secretion of FSH (by negative feedback) and begin secretion of LH (by positive feedback). The decrease in FSH will, in turn, decrease the production of estrogen. When the concentration of LH in the blood reaches a certain level, ovulation occurs; that is, one mature follicle (a Graafian follicle) ruptures, releasing a mature egg. Ovulation usually occurs at about the middle of the menstrual cycle.
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luteal stage
After ovulation, LH causes the ruptured follicle to fill with cells, forming the corpus luteum (yellow body). It begins to secrete the hormone progesterone, which maintains the continued growth of the endometrium. The corpus luteum also produces estrogen, which accounts for the rise in this hormone level after ovulation. As the concentration of estrogen and progesterone rise to a certain level, they in turn inhibit the secretion of FSH and LH, respectively (negative feedback). This stage lasts about 14 days.
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menustration phase
If fertilisation does not occur, the corpus luteum breaks down. This results in a decrease in the level of progesterone and estrogen. With a drop in the progesterone level, the thickened lining of the uterus can no longer be maintained, and it breaks down. As a result, the extra layers of the endometrium lining, the unfertilised egg and a small amount of blood pass out of the body through the vagina. This lasts about 3–5 days. While menstruation is occurring, the amount of estrogen in the blood falls, reducing the inhibitory effect of estrogen on FSH secretion. The pituitary gland then increases its output of FSH, a new follicle starts maturing, and the cycle starts again.
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progesterone is produced
ovary
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estrogen is produced
ovary
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FSH and LH are produced
pituitary
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he menstrual cycle. The letters a–d refer to the explanations below.
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role ofprogesterone
Rises to a peak towards the end of the follicular phase; stimulates repair of the endometrium and an increase in FSH receptors on ovary cells
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role of estrogen
Rises to a peak towards the end of the follicular phase; stimulates repair of the endometrium and an increase in FSH receptors on ovary cells
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role of FSH
Rises to a sudden peak towards the end of the follicular phase; stimulates completion of meiosis in the oocyte and thinning of the follicular wall, so that ovulation can occur. After ovulation, it stimulates the development of the remaining part of the Graafian follicle into the corpus luteum (by causing an increase in the number of follicle cells), which secretes estrogen (this is an example of positive feedback) and progesterone
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role of LH
Rises to a sudden peak towards the end of the follicular phase; stimulates completion of meiosis in the oocyte and thinning of the follicular wall, so that ovulation can occur. After ovulation, it stimulates the development of the remaining part of the Graafian follicle into the corpus luteum (by causing an increase in the number of follicle cells), which secretes estrogen (this is an example of positive feedback) and progesterone
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In the human menstrual cycle, which hormone causes the wall of the follicle to develop after ovulation and secrete more progesterone?
LH
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Which hormonal event causes ovulation to occur in the human menstrual cycle?
a quick rise in LH
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why might couples go for IVF
Woman with blocked fallopian tubes
Woman cannot produce healthy eggs
Man does not produce enough sperm for fertilisation to take place
Man suffering from erection problems
Genetic predisposition of one parent toward certain health problems
Couple is unable to conceive normally.
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steps in IVF
Step 1a: The woman is given a drug (or drugs) to suppress her natural cycle by suspending her normal secretion of hormones. She can administer them herself in the form of a daily injection or a nasal spray. The drug treatment continues for about 2 weeks.
Step 1b: FSH and LH are injected at a higher dose than normal for around 12 days to stimulate the production of a number of ova (egg cells), called superovulation. The clinic monitors progress throughout the drug treatment through vaginal ultrasound scans and, possibly, blood tests.
Step 2: Between 34 and 38 hours before the eggs are due to be collected, the woman will be given a hormone injection to help the eggs mature (this is likely to be human chorionic gonadotrophin). Eggs are then usually collected from the ovaries by using ultrasound guidance while the person is sedated. A hollow needle is attached to the ultrasound probe and is used to collect the eggs from the follicles in each ovary.
Step 3: A sperm sample is collected from the woman's partner and checked for viability.
Step 4: The eggs are mixed with the partner's or the donor's sperm and cultured in the laboratory for 16–20 hours after which they are checked for signs of fertilisation. (Sperm can also be injected directly into the egg, as shown in the alternate picture on the right at number 4 in the diagram.) Eggs that are fertilised (now called embryos) are grown in the laboratory incubator for up to 6 days. The embryologist will monitor the development of the embryos and the best will then be chosen for transfer. The remaining embryos of suitable quality are frozen for future use.
Step 5: If the woman is under the age of 40, one or two embryos are implanted in the uterus at the appropriate time in her menstrual cycle. But, if she is older than 40 years, a maximum of three may be used. The number of embryos transferred is restricted because of the risks associated with multiple births.
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arguments in favour of IVF
Infertile families can have a baby
Embryos can be screened for genetic anomalies and other disorders
Increases understanding of human reproduction
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arguements against IVF
Not all embryos are used, and some are destroyed
IVF often results in multiple births, which may be an increased risk for mother and babies
IVF is not considered 'natural', so it is not condoned by some religious groups
Women may be at risk because of hormonal injections
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Which hormones are administered in IVF to induce superovulation (production of more eggs than normal)?
FSH and LH
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hwo did harvey discover fertilisation
Harvey used a scientific approach, observing and dissecting female deer in the mating season to ascertain if small embryos could be found immediately after fertilisation. He theorised that the 'seed and soil' theory put forward by Aristotle could not be true, because he found no small embryos in the uterus of female deer after fertilisation. However, Harvey could not fully explain how development occurred as he was unable to see any embryo until many weeks after fertilisation: the instruments at his disposal at that time were not sophisticated enough to allow him to see gametes and the early stages of embryos. Harvey used only a magnifying glass: compound microscopes were not invented until after his death.
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What evidence allowed Harvey to conclude that Aristotle's theory was incorrect?
ack of proper embryos in female deer that had recently mated.
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what was aristoltles therpy abotu fertilisation
the man produces a seed which develops into an egg, which then further develops into an embryo with the help of menstrual blood.
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